Michael Bös

An NS3 protease inhibitor with antiviral effects in humans infected with hepatitis C virus

Hepatitis C virus (HCV) infection is a serious cause of chronic liver disease worldwide with more than 170 million infected individuals at risk of developing significant morbidity and mortality. Current interferon-based therapies are suboptimal especially in patients infected with HCV genotype 1, and they are poorly tolerated, highlighting the unmet medical need for new therapeutics. The HCV-encoded NS3 protease is essential for viral replication and has long been considered an attractive target for therapeutic intervention in HCV-infected patients. Here we identify a class of specific and potent NS3 protease inhibitors and report the evaluation of BILN 2061, a small molecule inhibitor biologically available through oral ingestion and the first of its class in human trials. Administration of BILN 2061 to patients infected with HCV genotype 1 for 2 days resulted in an impressive reduction of HCV RNA plasma levels, and established proof-of-concept in humans for an HCV NS3 protease inhibitor. Our results further illustrate the potential of the viral-enzyme-targeted drug discovery approach for the development of new HCV therapeutics.

Discovery of a potent and selective noncovalent linear inhibitor of the hepatitis C virus NS3 protease (BI 201335).

C-Terminal carboxylic acid containing inhibitors of the NS3 protease are reported. A novel series of linear tripeptide inhibitors that are very potent and selective against the NS3 protease are described. A substantial contribution to the potency of these linear inhibitors arises from the introduction of a C8 substituent on the B-ring of the quinoline moiety found on the P2 of these inhibitors. The introduction of a C8 methyl group results not only in a modest increase in the cell-based potency of these inhibitors but more importantly in a much better pharmacokinetic profile in rats as well. Exploration of C8-substitutions led to the identification of the bromo derivative as the best group at this position, resulting in a significant increase in the cell-based potency of this class of inhibitors. Structure-activity studies on the C8-bromo derivatives ultimately led to the discovery of clinical candidate 29 (BI 201335), a very potent and selective inhibitor of genotype1 NS3 protease with a promising PK profile in rats.

Discovery of BI 224436, a Noncatalytic Site Integrase Inhibitor (NCINI) of HIV-1

An assay recapitulating the 3 processing activity of HIV-1 integrase (IN) was used to screen the Boehringer Ingelheim compound collection. Hit-to-lead and lead optimization beginning with compound 1 established the importance of the C3 and C4 substituent to antiviral potency against viruses with different aa124/aa125 variants of IN. The importance of the C7 position on the serum shifted potency was established. Introduction of a quinoline substituent at the C4 position provided a balance of potency and metabolic stability. Combination of these findings ultimately led to the discovery of compound 26 (BI 224436), the first NCINI to advance into a phase Ia clinical trial.

Discovery of a 1,5-dihydrobenzo[b][1,4]diazepine-2,4-dione series of inhibitors of HIV-1 capsid assembly.

The discovery of a 1,5-dihydrobenzo[b][1,4]diazepine-2,4-dione series of inhibitors of HIV-1 capsid assembly is described. Synthesis of analogs of the 1,5-dihydrobenzo[b][1,4]diazepine-2,4-dione hit established structure-activity relationships. Replacement of the enamine functionality of the hit series with either an imidazole or a pyrazole ring led to compounds that inhibited both capsid assembly and reverse transcriptase. Optimization of the bicyclic benzodiazepine scaffold to include a 3-phenyl substituent led to lead compound 48, a pure capsid assembly inhibitor with improved antiviral activity.

5-HT6 receptor antagonists: lead optimisation and biological evaluation of N-aryl and N-heteroaryl 4-amino-benzene sulfonamides

RO-04-6790 (6a) has been identified in a random screen for 5-HT(6) receptor antagonists. In a medicinal chemistry optimisation program a series of analogs comprising N-heteroaryl- and N-arylbenzenesulfonamides have been synthesised and investigated for their binding affinity. Compounds with a logD profile indicative of brain penetration have been subjected to in vivo testing for reversal of a scopolamine-induced retention deficit in a passive avoidance paradigm.

Preclinical Profile of BI 224436, a Novel HIV-1 Non-Catalytic Site Integrase Inhibitor

ABSTRACT BI 224436 is an HIV-1 integrase inhibitor with effective antiviral activity that acts through a mechanism that is distinct from that of integrase strand transfer inhibitors (INSTIs). This 3-quinolineacetic acid derivative series was identified using an enzymatic integrase long terminal repeat (LTR) DNA 3′-processing assay. A combination of medicinal chemistry, parallel synthesis, and structure-guided drug design led to the identification of BI 224436 as a candidate for preclinical profiling. It has antiviral 50% effective concentrations (EC50s) of <15 nM against different HIV-1 laboratory strains and cellular cytotoxicity of >90 μM. BI 224436 also has a low, ∼2.1-fold decrease in antiviral potency in the presence of 50% human serum and, by virtue of a steep dose-response curve slope, exhibits serum-shifted EC95 values ranging between 22 and 75 nM. Passage of virus in the presence of inhibitor selected for either A128T, A128N, or L102F primary resistance substitutions, all mapping to a conserved allosteric pocket on the catalytic core of integrase. BI 224436 also retains full antiviral activity against recombinant viruses encoding INSTI resistance substitutions N155S, Q148H, and E92Q. In drug combination studies performed in cellular antiviral assays, BI 224436 displays an additive effect in combination with most approved antiretrovirals, including INSTIs. BI 224436 has drug-like in vitro absorption, distribution, metabolism, and excretion (ADME) properties, including Caco-2 cell permeability, solubility, and low cytochrome P450 inhibition. It exhibited excellent pharmacokinetic profiles in rat (clearance as a percentage of hepatic flow [CL], 0.7%; bioavailability [F], 54%), monkey (CL, 23%; F, 82%), and dog (CL, 8%; F, 81%). Based on the excellent biological and pharmacokinetic profile, BI 224436 was advanced into phase 1 clinical trials.

Discovery of the First Thumb Pocket 1 NS5B Polymerase Inhibitor (BILB 1941) with Demonstrated Antiviral Activity in Patients Chronically Infected with Genotype 1 Hepatitis C Virus (HCV)

Combinations of direct acting antivirals (DAAs) that have the potential to suppress emergence of resistant virus and that can be used in interferon-sparing regimens represent a preferred option for the treatment of chronic HCV infection. We have discovered allosteric (thumb pocket 1) non-nucleoside inhibitors of HCV NS5B polymerase that inhibit replication in replicon systems. Herein, we report the late-stage optimization of indole-based inhibitors, which began with the identification of a metabolic liability common to many previously reported inhibitors in this series. By use of parallel synthesis techniques, a sparse matrix of inhibitors was generated that provided a collection of inhibitors satisfying potency criteria and displaying improved in vitro ADME profiles. Cassette screening for oral absorption in rat provided a short list of potential development candidates. Further evaluation led to the discovery of the first thumb pocket 1 NS5B inhibitor (BILB 1941) that demonstrated antiviral activity in patients chronically infected with genotype 1 HCV.

Blunting the Swiss army knife of hepatitis C virus: inhibitors of NS3/4A protease.

Publisher Summary Hepatitis C virus (HCV) infection continues to be a serious disease with a large unmet clinical need. There has been substantial progress in the HCV virology and in the development of HCV protease inhibitors, in particular, as this topic was last reviewed in this series. The replicon has become a standard tool for the evaluation of inhibitor efficacy in cells, and reports of reproducible in vitro viral replication and useful transgenic animal models for HCV disease are beginning to emerge.

Conformation-Based Restrictions and Scaffold Replacements in the Design of Hepatitis C Virus Polymerase Inhibitors: Discovery of Deleobuvir (BI 207127)

Conformational restrictions of flexible torsion angles were used to guide the identification of new chemotypes of HCV NS5B inhibitors. Sites for rigidification were based on an acquired conformational understanding of compound binding requirements and the roles of substituents in the free and bound states. Chemical bioisosteres of amide bonds were explored to improve cell-based potency. Examples are shown, including the design concept that led to the discovery of the phase III clinical candidate deleobuvir (BI 207127). The structure-based strategies employed have general utility in drug design.

Discovery of a novel series of non-nucleoside thumb pocket 2 HCV NS5B polymerase inhibitors.

A novel series of non-nucleoside thumb pocket 2 HCV NS5B polymerase inhibitors were derived from a fragment-based approach using information from X-ray crystallographic analysis of NS5B-inhibitor complexes and iterative rounds of parallel synthesis. Structure-based drug design strategies led to the discovery of potent sub-micromolar inhibitors 11a-c and 12a-c from a weak-binding fragment-like structure 1 as a starting point.